Bark-type fuel feeder with vibrating proportioning table and flow dividing means



Aug. 21, 1962 M. o. FUNK 3,050,202

' BARK-TYPE FUEL FEEDER WITH VIBRATING PROPORTIONING TABLE AND FLOWDIVIDING MEANS Filed Nov. 18. 1958 4 Sheets-Sheet 1 24 0ufpuf Steam -/8Fuel v Supply /-28 /.9\

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BARK-TYPE FUEL FEEDER WITH VIBRATING PROPORTIONING TABLE AND FLOWDIVIDING MEANS Filed Nov. 18. 1958 4 Sheets-Sheet 2 Fig. 3.

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BARK-TYPE FUEL. FEEDER WITH VIBRATING PROPORTIONING TABLE AND FLOWDIVIDING MEANS Filed Nov. 18. 1958 4 Sheets-Sheet 4 VibratingProportioning Feeder Table INVENTOR Max 0. Funk ATTORNEY tits I Myinvention relates to the feeding and burning of bark and other cellulosefuels of similar character and it has special reference to improvedfeeder facilities by the aid of which such bark and wood-type fuels cansuccessfully be delivered to and burned in furnaces for the generationof steam and other purposes.

Broadly stated, the object of my invention is to enable bark and othercomparable fuels to be so fed into a furnace more uniformly andotherwise more satisfactorily than has been possible heretofore.

A more specific object is to produce a continuous flow of such fuelsinto the furnace under conditions when the fuel is supplied at anerratic rate that normally results in fuel delivery pulsations which arehighly objectionable.

Another object is to achieve such dependable uniformity in the feedingof bark and other fibrous fuels into furnaces which utilize a pluralityof spreader-type injectors that are positioned substantially above abottom grate of the furnace and that serve to bring the fuel into thefurnace combustion chamber.

A further object is to provide such multi-spreader type furnaces withnew and improved feeder apparatus which upon receiving the bark or otherfuel at a non-uniform or variable rate serves to deliver that fuel tothe several furnace injectors in streams which are of equal size and ineach of which the original supply rate variations mentioned above havebeen evened out if not completely eliminated.

Other objects and advantages will become apparent from the followingdescription of an illustrative embodiment of the invention when taken inconjunction with the accompanying drawings wherein:

FIG. 1 is a longitudinal section through a steam generating furnace thatis equipped with fuel feeding apparatus wherein my inventiveimprovements are incorporated;

FIG. 2 is a section in front elevation through my new feeder apparatus,as viewed from line 22 of FIG. 1, showing further details of thisimproved equipment;

FIG. 3 is a top plan view, taken from line 33 of FIG. 2, showing thefurnace front wall with the several fuel injectors therein, and also aportion of the feeder;

FIG. 4 is a view in side elevation, taken on line 4-4 of FIG. 3,indicating how vibration is imparted to my new proportioning platform ortable and to associated parts of the feeder;

FIG. 5 is a top plan view, taken from line 5-5 of FIG. 4, of thevibrating platform and flow-dividing channel elements of FIG. 4;

FIG. 6 is a simplified perspective representation of the entire feederassemblage as interposed between the fuel-supply source and the severalfurnace injectors; and

FIG. 7 is an enlarged showing of the entrance to one of the, injectorfeed chutes and of the bars that are positioned thereacross to preventunduly large pieces of fuel from passing into the chute.

The Illustrative Furnace to Which the Bark Fuel 1s Fed for BurningTherein The fuel feeder improvements of my invention are disclosed byFIG. 1 and the other drawing views as being utilized with a steamgenerator furnace whose combustion chamber C has fuel in the form ofwood bark or the 3,fi5,22 Patented Aug. 21, 1962 like introducedthereinto by five spreader injectors S1S2-S3$4-S5. In the arrangementshown, these fuel Spreaders S are mounted in the furnace front wall 10at an elevation substantially above a traveling stoker grate 6 at thefurnace bottom. All five sets of the spreader blades may be carried on acommon drive shaft 8 that is rotated by a motor 9 at some suitable speedsuch as several hundred revolutions per minute; or each set of spreaderblades may be equipped with an individual drive motor.

In gravitating downwardly into and successively through tangential airswirls represented at 11l2-13 14, the so introduced pieces of bark orother fuel are kept in suspension for a substantial length of time.During that time the finer fuel particles are fully burned, while thelarger fuel pieces in partly burned state fall upon the traveling grate6 where combustion thereof is com pleted. Ash resulting from suchburning of the larger fuel pieces falls from the discharge end of grate6 into a disposal passage 16.

Hot combustion gases produced by this burning of the bark or other fuel(both on the grate and in suspension) rise upwardly through furthertangential air swirls 15 (only one is shown here); and after reachingthe upper portion of furnace chamber C those gases leave the furnace viaflow to the right into a discharge passage 17 that leads to dustrecovery apparatus shown generally at 25, and thence to the furnacestack (not shown).

Water tubes 18 lining all four walls of the furnace chamber C areconnected, via downcomer 19 and other conventional elements, intocirculation with a steam and Water drum 20 at the furnace top. Byabsorbing heat from the burning fuel and hot combustion gases thesetubes 18 convert the boiler water therein into steam which risestherethrough and collects in drum 20. From the drum that generated steamflows via conduit 21 into and through superheater sections 22 and 23,and thence via output conduit 24 to a turbine (not shown) or other pointof use.

Explanation of the advantages that result from interposing tangentialair swirls such as 11-121314 between high-set fuel Spreaders such as51-85 and a traveling grate such as 6 at the furnace bottom is given byUS. Patent 2,483,728 which issued on October 4, 1949 to A. L. Glaeserand which is entitled Method and Apparatu for Burning High MoistureContent Fue Especially significant benefits to the efficiency both offuel combustion and of steam generation are realized when this burningtechnique is applied to cellulose fuels of high moisture content such asthe wood bark here under consideration.

Supply of Bark to the Fuel Feeder Typically Is Erratic Furnaces of thetype just described by reference to FIG. 1 find extensive use in papermill and other comparable installations where wood materials such aslogs are converted into various products such as the pulp from whichpaper is manufactured. Such logs as brought from the forest first havethe bark removed therefrom. This removal operation produces largequantities of bark, which takes the form of pieces of widely assortedsizes, shapes and lengths. It is with the problem of burning such barkin furnaces of the FIG. 1 type that the present invention is concerned.

This bark is taken from the de-barking machines (not shown) throughwhich the logs are passed, is dropped into a suitable fuel supply hopperwhich is represented at 28 in each of FIGS. 1, 2, 3 and 6 and which islocated somewhere between the debarking drums and the furnace C. In manyinstances hopper 28 may be a considerable distance from the furnace,such as feet or more. As shown it utilizes a screw or spiral member 29by which the assorted pieces of bark are discharged from the hopper 28upon the top of a belt 30 that runs to the furnace location. That belt30, in turn, delivers the fuel via a cas-' ing 32 upon the entrance endof a proportioning table K which is incorporated into my new feederapparatus in the novel and advantageous manner to be describedpresently.

The bark fuel so delivered via hopper 28 and screw 29 upon the supplybelt 30 is not always in the form of a uni- Furnace C RespondsUnfavorably to Erratic Fuel Delivery When conventional feeder apparatusis utilized between supply belt 30 and the spreader injectorsS1S2-S3S4S5 of the FIG. 1 furnace, such a non-uniform distribution(separated piles F) of the incoming bark fuel along the length of saidbelt 30 will be accompanied by a delivery of that fuel to thosespreaders S and thence into the furnace C which is correspondinglyerratic and non-uniform.

The effect on the furnace of such erratic fuel feeding is not good. Eachtime that a concentrated quantity (such as the contents of one of thepiles F) of the fuel comes into combustion chamber C via the spreadersS, the intensely accelerated burning produces a pufiing action that isaccompanied by sharp rises in the heat release and in the internalfurnace pressure and in the volume of hot gases which pass through thedust recovery apparatus 25 on their way to the furnace stack.Overloading of said dust recovery apparatus 25 and associated fly ashreinjection equipment 26 is found to occur on the occasion of each ofthese intense furnace pufis; moreover, the furnace walls and casing aresubjected to objectionable mechanical strains, produced by the recurringpressure rises in combustion chamber C, when the fuel is brought intothe furnace in such an erratic and non-uniform manner.

Avoidance of such erratic fuel feed is therefore an objective which ishighly to be desired but which prior to the availability of my inventionhas not been attainable in any commercially satisfactory manner.

The New Fuel Feeder Apparatus With Proportioning Table K Referring toFIGS. 2 through 7, my new feeder apparatus utilizes the earliermentioned proportioning Table K plus an associated floor 33 of lowerelevation that has upstanding flow-dividing partitions 3435-3637 withouter side walls 38 and 39. Between these walls and partitions there areformed five fuel channels represented as respectively communicating withthe spouts or conduits 4142' 434445 that lead to the fivespreader-injectors S1S2S3-S4S5 of the FIG. 1 furnace C.

Screen bars shown at 4748 permit pieces of the bark within an acceptablesize range to drop from said feeder channels downwardly through openingsin floor 33 and thence into said five spreader supply spouts 41-45,while at the same time these bars reject bark pieces which areexcessively large and which thereupon advance to the discharge end ofthe feeder (right in FIGS. 1-2-3-4-5) where they are manually collectedand disposed of by an operator (not shown).

From FIGS. 2 through 6 it will be seen that the side walls 38 and 39 ofthe partitioned feeder floor 33 continue back therefrom along the twosides of the proportioning Table K and join with an upstandingtransverse wall 55 at the extreme rear end of the table (beneath thefuel entrance casing 32); also that at the opposite or fuel delivery endof Table K there is a second transverse wall 56 which extends downwardlyfrom the table level to the lower level of feeder floor 33 and whichserves to close the rear ends of the five fuel channels as formed abovesaid floor 33 by the partitions 34353637.

The entire assemblage consisting of proportioning Table K and thepartitions 3435-3637 plus their floor 33 and side walls 38-39 isarranged to vibrate in such a way that bark or other fuel fed upon thetable at entrance casing 32 will slowly advance along the full tablelength, and after dropping from the tables discharge end (right in FIGS.1 through 5) into the five channels formed by partitions 34-353637 willfurther advance through those channels to the floor 33 openingstherealong that respectively are above the supply spouts for theassociated fuel spreaders S.

In the illustrative vibrating arrangement of FIGS. 2-345, thepartitioned floor 33 is supported by leaf springs 50 which are inclinedto the rear in the manner indicated; the integrally associatedproportioning Table K is similarly supported by leaf springs 51 'whichalso are inclined to the rear; and through an eccentric drive 52, plus alink connection 53 with the underside of platform K, the aforementionedassemblage is repeatedly pushed upwardly ahead and withdrawn downwardlyback at some suitable frequency such as 25 or 60 cycles per second. Ascan be seen from FIGS. 2 and 4, these push and withdraw movements causethe floor 33 and Table K to flex their support springs 5t 51 around therepresented stationary mountings at the lower ends of those springs.

By each such upward-forward movement, all of the bark or other fuel ontable K and floor 33 is advanced by a small amount forwardly, or to theright in FIGS. 234-5; and during each subsequent downward-rear movement,this advancement by the fuel is lost only slightly if at all. The resultthus is a slow but steady forward moving of said fuel along the tableand floor due to subjection of these assemblage parts to vibratoryaction such as is explained above.

As the description proceeds it will become apparent that other means forinducing comparable vibrations in the assemblage parts also may besubstituted and utilized in the improved feeder apparatus of myinvention.

New Proportioning Table K Evens Out Supply Variations Wood bark or otherfuel F received upon proportioning table K from supply belt 30 viacasing 32 in the form of a primary supply stream is spread by the tablevibrations laterally across the table width into a layer of uniformthickness. Upon arrival at the tables discharge end (right in FIGS.2-34-5) the material of this layer drops into the live fuel channels(formed by partitions 34353637) and thereby supplies those channels withindividual streams of the fuel. These five divided streams aresubstantially equal, due to the uniformity in fuel layer thicknessacross the table K (between side walls 38 and 39) at its discharge end.Each of said five streams, in turn, moves forwardly along the vibratingfeeder floor 33 and drops from its channel through the floor openingthat is above the duct (41 or 42 or 4-3 or 44 or '45) for the associatedfurnace spreader S1 or S2 or S3 or S4 or S5.

The lateral-spreading function just explained is accomplished in only acomparatively short length of the proportioning table K, which need beonly the same as or even less than the width W (see FIGS. 5 and 6) ofthat table. Under optimum conditions, therefore, wherein the fuel comesupon the table K from supply belt 30 as a uniform and non-erraticprimary stream, the length of this table can be comparatively shortwithout sacrifice in the quality of feeder performance.

Prior to my invention the length of a proportioning table such as K waslimited to not more than the tables Width dimension W. But, as alreadypointed out, fuel feeding and firing installations of the type hereinconsidered frequently have the unhogged bark or other fuel brought tothe FIG. 1 furnace as anon-uniform erratic primary stream of which thespaced piles of fuel F on supply belt 30 is typical; and in thosesituations a feeder proportioning table of the limited length juststated is ineffective for evening out objectionable hills and valleys inthe rate of original or primary fuel supply, as from belt 30.

In an effort to overcome the foregoing difficulty, I conducted a seriesof experiments aimed at determining whether a proportioning table suchas K might somehow be made to average out primary fuel supplyunevennesses in an advantageous way. Fuel material of the wood bark typewas used during these experiments. They clearly indicated that if thelength dimension L of table K is increased to the general order of threeor more times the width dimension W, the table then is eminentlyefiective for converting an uneven supply of fuel upon its receiving end(under casing 32) into a relatively uniform and even rate of materialdropping from its discharge edge (right in FIGS. 2-345) into the fuelchannels between partitions 3435--3637 along the vibrating feeder floor33.

On the basis of these experimental findings, I caused to be built thefull-sized feeder which the drawings hereof show and in which theproportioning table K has a length L that is substantially three timesits width W. This so-improved feeder then was made a part of the furnaceinstallation of FIG. 1 and there subjected to the severe tests ofpractical operation.

These tests have convincingly confirmed what my preliminary experimentshad predicted; namely, that even though the wood bark or other fuelcomes into the feeder in the form of time-spaced concentrated batchessuch as FIGS. 1, 3 and 6 represent at F, the vibrating action ofproportioning table K when carried out during the greatly increasedtable length L does in fact average out the original supply unevennessesin a most advantageous way. Each individual pile F of the supplied fuelin advancing along the vibrating surface of said lengthened table Kspreads itself out thereover in the end-to-end direction as well as fromside to side; and due to the prolonged continuance of this action whichmy elongated table K makes possible, each such individual fuel pile Fhas been distributed over a considerable span of the table by the timeit reaches the tables discharge end (right in FIGS. 2-3-4-5).

Practical Operating Advantages Successive piles of the fuel F as droppedfrom belt 30 upon the entrance end of elongated table K in timespacedrelation thus tend to merge one into the other as they progress alongthe vibrating table surface; so that upon arrival at the discharge endthe original supply unevennesses have been either fully eliminated orgreatly minimized.

The FIG. 1 furnace C when supplied with wood bark or other fuel by myimproved feeder is accordingly no longer subjected to the objectionablepuffing which an earlier section of this specification has described,and the dust recovery and fly ash reinjection portions 25-26 of theinstallation are no longer periodically overloaded by reason of suchpufling.

My inventively new feeder thus betters the performance of the overallfurnace installation wherein the improved feeder is employed; moreover,it broadens the capability of the feeder itself for use in possibleother applications wherein elimination of fuel supply unevennesseslikewise is important.

Summary The inventive improvements herein disclosed and claimed aretherefore extensive in their adaption and hence are not to be restrictedto the specific form here disclosed by way of illustration.

What I claim is:

1. In a system comprising a furnace having a combustion chamber that isequipped with a plurality of fuelinjecting spreaders and fuel conveyingmeans which bring to the location of said furnace cellulose fuel such aswood bark in the form of a primary supply stream that is nonuniform anderratic both as to flow volume and continuity, the combination of feederapparatus for receiving said non uniform primary stream of supply fueland for converting it into a plurality of divided individual streamswhich are equal in size and relatively non-interrupted in flowcontinuity and which are respectively delivered by the apparatus to thefurnaces said plurality of fuelinjecting spreaders, said feederapparatus comprising an assemblage of parallel flow channels which arein respective supply communication with said plurality of furnacespreaders and which have upstream ends that are defined by a floor plusleft and right side walls and intervening partitions upstanding from thefloor; a proportioning table which extends away from said upstreamchannel ends in a horizontal plane that is at an elevation above thelevel of said fioor and at least as high as the top edges of the saidpartition upstream ends and which is flanked by left and rightupstanding side walls that merge with the corresponding side walls ofsaid channel assemblage the discharge edge of said table being in feedcommunication with said upstream ends of all of said flow channels andthe opposite or receiving end of the table being in feed communicationwith said fuel conveying means; means for imparting both to said tableand to said flow channel assemblage a form of vibration which slowlyadvances said received fuel along said extended length of the tabletowards said discharge edge thereof and thence over that edge down intothe upstream ends of all of said assemblage channels; the length of saidtable being such with respect to the width thereof that the vibrationsproduced in the table by the vibration means will spread the nonuniformprimary stream of supply fuel evenly thereon, such that said fuel isspaced substantially evenly across the entire table width and length, assaid fuel progresses along the length of the table, said fuel arrivingat said discharge edge in a substantially continuous layer of uniformthickness.

2. The system set forth in claim 1 wherein said proportioning table isprovided at its fuel-receiving end with a transverse wall that extendsbetween said left and right side walls of the table and stands upwardlyfrom the table so as to prevent fuel as delivered upon the table surfacein the vicinity of said receiving end from spilling over the edge ofthat end.

3. The system set forth in claim 1, wherein the recited floor of saidfuel channel assemblage lies in a generally horizontal plane and isprovided with openings through the individual channel portions of thatfloor, and further wherein ducts extend down from those channel openingsto the said plurality furnace spreaders and serve to carry fuel fromthose channels to those spreaders.

4. The system set forth in claim 1, wherein the length of said table isat least three times the width thereof.

References Cited in the file of this patent UNITED STATES PATENTS1,060,943 Rehak May 6, 1913 1,219,067 Bailey Mar. 13, 1917 2,564,683Frisch Aug. 21, 1951 2,863,577 Kyle Dec. 9, 1958 OTHER REFERENCES SimBurn Bark & Coal (Hansen & Copian), published in Tappi, vol. 38, No. 10,October 1955.

